Passing the exam does not mean you will be advanced. There are 3 things that can happen with an advancement exam: Fail, Pass not Advanced (PNA), or passed and advanced. Basically, there are a certain number of people who can be advanced, so the people with the highest point totals, taking into account score on the test, awards received, how many exams you have previously PNA'd, and performance evaluation score will be advanced. I would not worry about only getting PNA on a first E-5 exam, as many of the E-5 slots are taken by people who STAR reenlist. During my time on my boat I knew several smart people who took several test attempts to advance. If he was scheduled and took the nuke version of his rate's advancement exam, his NEC is likely fine, but if he is in doubt he could check with the appropriate admin types on his ship to verify he has the correct NEC.